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Schilling JD, Martin SM, Hung CS, Lorenz RG, Hultgren SJ.Schilling JD, et al.Proc Natl Acad Sci U S A. 2003 Apr 1;100(7):4203-8. doi: 10.1073/pnas.0736473100. Epub 2003 Mar 24.Proc Natl Acad Sci U S A. 2003.PMID: 12655047Free PMC article.